Nuts. I bet it would have failed a lot sooner with a sustained rate of fire.
My grandfather was in Korea at the chosin when the Chinese attacked. He said the snow covered mountains had chinamen pouring down them like chocolate down a scoop of vanilla ice cream. They didn't have time to change barrels and fired until the barrels began to droop from heat.
Your grandfather must have been a hell of a guy if he got out of that hell on earth that was the chosin reservoir.
Last winter I swung by home depot in uniform to get some wood filler. A vet hobbled after me and thanked me for my service. I noticed he was wearing Korean conflict veteran hat with a chosin reservoir pin. He was also missing fingers likely from frost bite. I told him if every service man stationed at JBLM shook his hand that wouldnt be enough thanks for what he and his comrades went through. He kind of teared up and i gave him a hug.
My Uncle was in Vietnam. The only time i heard him speak of the his experience over there came up in a conversation about barrel heat on hunting rifles. He said one of his buddies was going home in a week. So he told him to give him all his magazines and keep his head down. Which emptied his and his own through his m16. He said the front sight of the rifle was glowing in the dark.